Page 231 - The Art of Designing Embedded Systems

21 8 THE ART OF DESIGNING EMBEDDED SYSTEMS

Use too many parentheses. Never let the compiler resolve prece-
dence; explicitly declare precedence via parentheses.
Never make assignments inside if statements. For example, don’t
write:

if ((foo = (char *) malloc(sizeof *foo)) == 0)
)
fatal ( “virtual memory exhausted” ;
instead. write:

foo = (char *) malloc(size0f *fool;
if (foo == 0)
fatal “virtual memory exhausted” 1
(
If you use # i f def to select among a set of configuration options,
add a final #else clause containing an #error directive so that the
compiler will generate an error message if none of the options has been
defined:

#ifdef sun
#define USE-MOTIF
#elif hpux
#define USE-OPENLOOK
#else
#error unknown machine type
#endif

Assembly Formatting

Tab stops in assembly language are as follows:

Tab 1: column 8
Tab 2: column 16
Tab 3: column 32

Note that these are all in increments of 8, for editors that don’t sup-
port explicit tab settings. A large gap-16 columns-is between the
operands and the comments.
Place labels on lines by themselves, like this:

label :
mov rl, r2 ; rl=pointer to I/O